Wet spinning of birefringent solutions of optically active polypeptide



1964 D. G. H. BALLARD ETAL 3,

WET SPINNING OF BIREFRINGENT SOLUTIONS OF OPTICALLY ACTIVE POLYPEPTIDEFiled May 8, 1962 lnven/ors Den/s George Ham/0 B0/l0rd James DennisGn'ffi/hrs James Wofson 5y f/ve/r affomeys United States Patent3,121,766 WET SPINNING (1F BRREFRIN GENT SOLUTIONS OF OPTIQALLY ACTIVEPOLYPEPTIDE Denis George Harold Ballard, Warwick, and James DennisGrilliths and James Watson, Maidenhead, England, assignors to CourtanldsLimited, London, England, a British company Filed May 8, 1962, Ser. No.193,667 Claims priority, application Great Britain May 9, 1961 '7Claims. (Cl. 264-202) This invention relates to the production ofartificial threads from polypeptides, and is particularly concerned withthe production of threads composed essentially of the optically activeforms of poly-gammamethyl glutamate as obtained by the polymerisation ofgamma-methyl glutamate N-carboxy anhydrides.

The Ballard patent application Serial Number 94,069 filed March 7, 196 1(a continuation-in-part application of applications Serial Numbers805,180 filed April 9, 1959, 9,153 filed January 22, 1960 and 27,260filed May 6, 1960 all now abandoned) describes and claims new crys'talline polypeptide fibres of which at least 90 percent by weight iscomposed of units of an optically active form of gamma-methyl glutamate(or of the corresponding ethyl glutamates) said fibre beingsubstantially in the beta configuration and exhibiting a substantialamount of orientation as determined by X-rays and said polymer having areduced viscosity of at least 1.4. Such fibres are produced by a processsuch as claimed in the Ballard application Serial Number 161,762. filedDecember 1, 1961, now Patent No. 3,089,749 and divided out of SerialNumber 94,069, the process comprising polymerising an optically activegamma-methyl glutamate N-carboxy anhydride in an organic liquid mediumwhich is a solvent for the polypeptide formed, the polypeptide beingcomposed of at least 90 percent by weight of units of the opticallyactive glutamate ester, extruding a solution of the polypeptide while itis still in the solvated state into a setting medium, for example acoagulating bath, so that the polypeptide is in the alpha configurationon extrusion and stretching the resultant fibre while it is still in thealpha configuration thereby converting the polypeptide substantiallyinto the beta configuration and orienting the fibre along its axis. Thepolymerisation processes described in the said applications SerialNumbers 94,069 and 161,762 produce spinning solutions of poly-gammamethyl glutamates generally containing from 6 to 9 percent of thepolypeptide.

The process of wet spinning the poly-gamma-rnethyl glutamate solutioncan be carried out readily for example using standard viscose machineryand the fibres obtained have very satisfactory textile properties.However, extrusion speeds in wet spinning with poly-methyl glutamates asdescribed in said applications Serial Numbers 94,069 and 161,762 havebeen rather low, for instance speeds of 16.8 metres per minute aredescribed in the examples, and it has not proved possible with the solutions described therein to improve the spinning speeds materially aboveabout 70 metres/minute. The term spinning speed is used in thisspecification to mean the linear speed at which the extruded filamentsare withdrawn from the coagulating bath by the first godet, reel orroller to which the filaments are passed when they leave the spinningbath.

From an economic point of view, it is clearly desirable that the outputof each spinning unit should be as high as possible. This isparticularly true of wet-spinning units which are appreciably moreexpensive than dryspinning units. However, other technicalconsiderations may make it desirable to use wet-spinning processes. Inorder to increase the output of a particular spinning machine, it isdesirable to increase the spinning speed as far as possible subjectgenerally to the two provisos that satisfactory and stable spinningconditions can be achieved and that the textile properties of the fibresobtained are satisfactory.

The present invention is directed particularly to the problem ofincreasing the spinning speed in the production of polypeptide fibres.By the present invention we have been able to achieve spinning speeds inthe polypeptide field of 140 to 30 0 metres per minute and even higherto produce commercially satisfactory textile fibres.

Investigations which we have carried out have shown that dilutesolutions of poly-gamma-methyl glutamates obtained as described in theabove-mentioned application Serial Number 94,069 are isotropic, that isto say that when a flat layer of the solution is placed between twocrossed Nicol prisms or Polaroid plates with a source of light beyondone of the prisms or plates, there is no transmission of light.

By carrying out the solvent polymerisation of the gamma-methyl glutamateN-carboxy anhydride at an ele vated temperature, and with an appropriateconcentration of the gamma-methyl glutamate N-carboxy anhydride in thesolvent medium, it has been found possible to produce more concentratedsolutions, for example solutions containing 14 percent by weight or moreof the poly-methyl glutamate. Unlike the dilute solutions referred to inthe previous paragraph, these concentrated solutions are birefringent,that is to say, they transmit light between two crossed prisms orplates. We have found that the birefringent solutions can be extruded athigh speeds, namely at least 140 metres per minute.

The difference in optical properties described in the precedingparagraph may be illustrated by the fact that the 7.5 percent solutionobtained as described in Example 1 of application Serial Number 94,069is isotropic whereas both the 15 and 16 percent solutions described inExample 1 below in this specification are birefringent. As a result ofour investigations it is apparent that there is a range of solutions ofthese polypeptides, which are those containing up to about 10 percent byweight of the polypeptides, which are substantially isotropic and. arange of solutions, which We believe to be those containing more thanabout 12 percent by Weight of the polypeptide, which are substantiallybirefringent, the solutions with concentrations in between these twolimits being a mixture of the two types of solution.

In its widest aspect, therefore, the present invention comprises aprocess for the production of fibres composed of polymers consisting ofat least percent by weight of units of an optically active form ofgammamethyl glutamate comprising extruding a birefringent solution ofthe polymer into a liquid coagulating bath at a spinning speed, ashereinbefore defined, of at least metres per minute, and stretching theresultant fibre while the polymer is still in the alpha configurationthereby converting the polymer substantially into the beta configurationand substantially orienting the fibre along its axis.

Our investigations have further shown that: under certain preferredspinning conditions, which are discussed more fully below, thebirefringent solutions can be wet spun at very high speeds, that is tosay at speeds of 140 to 300 metres per minute, preferably to 260 metreser minute, to produce textile fibres having particularly desirabletensile properties which we define in this specification as those havingdry tenacities of at least 2 grams per denier and a dry extensibility ofat least 10 percent.

The present invention is applicable to the opticallyactive form of thepolypeptides prepared from either of the optically-active gamma-methylglutamates, both homopolymers and copolymers containing at least 90percent by weight of one of the optically-active glutamate u esters asdescribed in the above-mentioned Ballard applications. For convenience,however the invention will now be described with particular reference tothe homopolymer of gamma-methyl-L-glutamate.

Garnrna-methyl-L-glutamate can be readily plymerised in a solventmixture such as methylene chlorideethyl acetate at elevated temperatureas described above to produce birefringent solutions containing, forexample, from 14 to 20 percent by weight of the polypeptide. Thesesolutions can be wet spun for example into acetone or ethyl acetate or amixture of the two liquids to form threads.

The fibres according to this invention are produced from polymersconsisting essentially of gamma-methyl- L- or D-glutamates having areduced viscosity of at least 1.4 so that the resultant threads obtainedwill have adequate tensile properties for normal textile purposes; thepolymers preferably have a reduced viscosity of at least 2.0. In thisspecification reduced viscosity is defined as where 1 is the specificviscosity of a solution having a concentration of C grams per 100 cc. ofsolution. The solvent used for all the reduced viscosity measurementsgiven in this specification was a 1 to 9 volume by volume mixture oftrifiuoroacetic acid and trichloroacetic acid.

When carrying out high speed spinning using the hirefringent type ofsolutions as described herein it has been found highly desirable inorder to obtain the desirable tensile properties as defined to haveregard to two factors namely (a) the viscosity of the spinning solution,(b) the pull-off ratio used in the spinning process.

As regards the viscosity of the spinning solutions, we have carried outspinning trials with birefringent solutions of the polypeptide havingviscosities ranging as far apart as from 56 to 10,008 poises.Viscosities through out this specification are measured at 25 C. Whenusing pull-off ratios known to be suitable for high speed spinning asdescribed below, the solution having the viscosity of 56 poises could bespun at high speeds to produce stretched fibres but the tensileproperties of the fibres deteriorated as the speed increased. On theother hand, solutions having viscosities ranging from 70 to as high as10,000 poises were found to be suitable for spinning at highspeedsconsistent with the production of fibres having the desirabletensile properties. However it is possible to obtain useful fibres byusing a spinning solution haying viscosities from 50 to 70 poises ifcare is taken to ensure that the spinning speed and pull-ofi ratio aresuit-able, but the properties of the fibers may deteriorate as the spinn-ing speeds are increased.

We have observed that even when using apparently identical conditionsfor the polymerisation step with identical quantities of the samereagents, the spinning solutions obtained have had widely dilferentviscosities, and even when polymerising a stock solution in two or moreparts under identical conditions the resulting spinning solutions arelikely to have widely differing viscosities. However, for the purposesof the invention the actual value of the viscosity is immaterialprovided that, in order to obtain the tensile properties as definedabove, the viscosity of the actual solution is at least 50 poises andpreferably at least 70 poises.

in wet spinning, the pull-oil ratio is defined as the rate at which thefilaments are withdrawn from the spirning bath by the first godet orother draw-off device divided by the linear rate of extrusion, bothrates being generally expressed as metres per minute. In general, wehave found that birefringent solutions of the polypeptide of suitableviscosity as explained above can be wet spun at speeds of as high as 260metres per minute but that the tensile properties of the threadsobtained after the required stretching operation depend markedly on thepulloif ratio used. At pull-off ratios of less than 1.0 the dry tenacityof the fibres obtained is usually less than 2.0 grams/ denier and thereis a linear decrease in the tenacity as the spinning speed increases. Ata pull-off ratio of 1.0 there is no reduction in tensile propertiesuntil speeds of about 180 metres per minute are reached but beyond thisspeed fibre properties deteriorate markedly. However at a pull-oh ratioof 1.2 the fibre properties are maintained at speeds up to 260 metresper minu e and at a pull-off ratio of 1.5 spinning speeds of as high as300 metres per minute may be used to produce high tenacity textilefibres. Accordingly, in carrying out this invention, the pull-off ratiois preferably at least 1.2 so that spinning speeds of 180 to 260 metresper minute may be used.

The present invention therefore includes a process for the production offibres having a tenacity of at least 2 grams per denier, and anextensibility of at least 10 percent composed of polymers consisting ofat least percent by weight of units of an optically active form ofgamma-methyl glutamate comprising extruding a birefringent solution ofthe polypeptide having a viscosity of at least 50 poises and preferablyat least 70 poises, the reduced viscosity of the polymer being at least1.4 and preferably at least 2, into a liquid coagulating bath at aspinning speed, as hereinbefore defined, of at least metres per minute,and at a pull-off ratio of at least 1.0, and preferably at least 1.2,and stretching the resultant libre while it is still in the alphaconfiguration thereby converting the polypeptide substantially into thebeta configuration and substantially orienting the fibre along its axis.

The polymerisation solvent used is preferably a methylene chloride-ethylacetate mixture containing a major proportion of methylene chloride, butother solvents or solvent mixtures as described in application SerialNumber 94,0 69 may be used. When solvents containing a major part ofmethylene chloride are used in the polymerisation, the polymerisationstep may conveniently be carried out at or near the boiling point (40C.) of methylene chloride, for example under refluxing conditions. Thepreferred coagulating liquid is acetone. The extrusion of the solutionmay be either vertical or horizontal, and may also be carried outaccording to the procedure known as tube-spinning as used in viscosespinning.

One form of apparatus suitable for spinning at high speeds awording tothe process of this invention is illustrated diagrammatically in theaccompanying drawing. As shown, the spinning solution is extrudedvertically upwards through a jet 1 by means of the usual type ofmetering pump (not shown) into a liquid 00- agulating bath '2. Theresulting filaments 3 are withdrawn from the bath by means of a threadadvancing reel 4- on which they are washed 'With acetone from a feedpipe 5, the acetone wash running down into the spinning bath via atrough '6. The filaments are then passed round a second reel 7, andwashed with water supplied by a pipe 8 on a third reel 9. They are thenpassed to another reel '10 and are stretched between the reels '9, 10.Reel 10 is partly enclosed in a container 12 to which warm air issupplied in order to dry the filaments. The filaments pass by Way of afinal reel 11 for collection on a conventional ring spinner 13. Theperipheral speeds of reels 4, 7 and 9 are substantially the same; thespeed of reel '4 deter-mines the spinning speed.

The reel 4 may be replaced by a godet which will then determine thespinning speed and the acetone wash effected on reel 7.

It is desirable when carrying out high speed spinning to provide one ormore suitable guides 14 for the filaments above the surface of thecoagulant in order to prevent excess carry-over of the coagulant,contaminated with solvent, by the filaments on to the first godet orreel.

For convenience in setting up, the reels and the metering pump arepreferably all driven together through a single infinitely variable gearbox so that the whole spinning line can be set up at a low speed atwhich the filaments can be manipulated conveniently, and the speed ofall the reels can then be increased to the desired high speed in unison.

The invention is illustrated by the following examples in whichpercentages are by weight.

Example I 24.5 parts of gamma-methyl-L-glutamate N-oarboxy anhydridewere dissolved in 100 parts of a mixture of 12 volumes of methylenechloride and 5 volumes of ethyl acetate. The solution was heated under areflux condenser to 40 C. and polymerisation was effected at 40 C. byadding 0.16 part of tri-n-butylarnine. The resultant polymer solutioncontained approximately 15 percent by weight ofpoly-garmna-methyl-Lglutamate. On degassing its concentration increasedto 16 percent.

The solution which had a viscosity of 140 poises was then extrudedvertically upwards into acetone as illustrated in the accompanyingdrawing. The solution was fed to a 20 x 2 mil hole jet by a meteringpump and the resultant filaments, after an immersion of 46 centimetres,were passed round a godet, and then on to a first thread-advancing reelwhere the filaments were washed in acetone and then to a second reelwhere the filaments were given a Water wash; both the reels had the sameperipheral speed as the godet. The pull-ofi ratio was 1.216 and thespinning speed, i.e. the peripheral speed or" the godet, was 260 met-resper minute.

From the second reel the filaments were passed to a third reel andbetween these reels they were stretched 80 percent in air to convert thepolypeptide into the beta configuration. The filaments were dried on thethird reel and collected on a ring spinner. The dry tenacity of thefibres was 2.8 grams/denier.

Using the same solution and the spinning conditions set out in thisexample with (a) a spinning speed of 180 metres per minute and a stretchof 80 percent and (b) an extrusion speed of 220 metres per minute and astretch of 80 percent, the tensile strengths of the fibres obtained were(a) 2.85 grams/denier and (b) 2.9 grams/denier.

Example 2 The same solution as used in Example 1 was extruded at anextrusion speed of 260 metres per mintue to form fibres which werewashed, stretched 80 percent and dried as described in Example 1 withthe exception that the pull-oil ratio used was 1.52. In this case thetensile strength of the fibres was 2.9 grams/ denier.

Using spinning speeds of 140, 180 and 220 metres per minute, similarfibres to those of Example 1 were obtained in all three cases.

Example 3 A solution of poly-gamma-methyl-L glutamate prepared asdescribed in Example 1 had a viscosity of 950 poises. It was extrudedinto acetone as described in Example 1 but with horizontal spinning at aspinning speed of 300 metres per minute through the jet positioned justbelow the surface of the coagulant, the fibres being Withdrawn from thebath by Way of a guide placed just above the surface of the acetone and48 cms. from the jet.

The dry tenacity of the fibres obtained after stretching 80 percent was2.5 grams/denier. At spinning speeds of 180, 220 and 260 metresrespectively, the corresponding tenacity figures were 2.35, 2.65 and2.65 grams/denie Example 4 A solution of poly-gamma-methyl-L-glutamateprepared as described in Example 1 had a. viscosity of 3,400 poises. Thesolution was then extruded vertically upwardly into ethyl acetatethrough a 20 x 2 mil hole jet using a metering pump. After an immersionpath of 40 cms. in the ethyl acetate bath, the resulting fibres werepassed over a series of thread-advancing reels as shown in the drawing,the stretch being percent. The pull-off ratio was 1.22 and the speed ofthe filaments on the first reel was 180 metres per minute. The filamentshad a dry tenacity of 2.36 grams per denier.

Example 5 A solution of poly-gamma-methyl-L-glutamate prepared asdescribed in Example 1 had a viscosity of 93 poises. The spin bath andspinning equipment were the same as those used in Example 1, except thata 60 x 2 mil hole jet was used. The spinning speed was 180 metres perminute. The pull-off ratio was 1.36. The fibres were stretched 70percent and then dried using air at 50 C. The dry tenacity of thefilaments was 2.75 grams/ denier and the extensibility was 14.7 percent.

Example 6 A solution of poly-gamma-methyl-L-glutamate prepared asdescribed in Example 1 had a viscosity of 1,400 poises. The spinningbath and equipment were the same as those used in Example 1. Thespinning speed was 140 metres per minute. The pull-off ratio was 1.25.The fibres were stretched 73 percent and then dried using air at 66 C.The resulting filaments 'had a dry tenacity of 3.31 grams per denier andan extensibility of 15.6 percent.

What we claim is:

1. A process for the production of polypeptide fibres consisting of atleast percent by weight of units of an optically active form ofgamma-methyl glutamate comprising extruding a birefringent solution ofthe polymer into a liquid coagulating bath at a spinning speed of atleast metres per minute and stretching the resultant fibre While thepolymer is still in the alpha configuration thereby converting thepolymer substantially into the beta configuration and substantiallyorienting the fibre along its axis.

2. A process as claimed in claim 1 wherein the polymer used is ahomopolymer of gamma-methyl-L-glutarnate.

3. A process for the production of polypeptide fibres having a tenacityof at least 2 grams per denier and an extensibility of at least 10percent, consisting of at least 90 percent by weight of units of anoptically active form of gammamethyl glutamate, comprising extruding abirefringent solution of the polymer having a viscosity of at least 50poises, the reduced viscosity of the polymer being at least 1.4, into aliquid coagulating bath at a spinning speed of at least 140' metres perminute and at a pull-off ratio of at least 1.0 and stretching theresultant fibre while the polymer is still in the alpha configurationthereby converting the polymer substantially into the beta configurationand substantially orienting the fibre along its axis.

4. A process for the production of polypeptide fibres having a tenacityof at least 2 grams per denier and an extensibility of at least 10percent, consisting of at least 90 percent by Weight of units of anoptically active form of gamma-methyl glutamate, comprising extruding abirefringent solution of the polymer having a viscosity of at least 70poises, the reduced viscosity of the polymer being at least 1.4, into aliquid coagulating bath at a spinning speed of at least 180 metres perminute and at a pull-oil ratio of at least 1.2, and stretching theresultant fibre while the polymer is still in the alpha configurationthereby converting the polymer substantially into the beta configurationand substantially orienting the fibre along its axis.

5. A process for the production of polypeptide fibres having a tenacityof at least 2 grams per denier and an extensibility of at least 10percent, consisting of at least 90 percent by weight of units of anoptically active form of gammamethyl glutamate, comprising extruding abiretringent solution of the polymer having a viscosity of at least 70poises, the reduced viscosity of the polymer being at least 2.0, into aliquid coagulating bath at a spinning speed of at least 180 metres perminute and at a pull-ofi? ratio of at least 1.2, and stretching theresultant fibre While the polymer is still in the alpha configurationthereby converting the polymer substantially into the beta configurationand substantially orienting the fibre along its axis.

6. A process for the production of polypeptide fibres consistingessentially of a homopolymer of gammarnethyl-L-glutamate having atenacity of at least 2 grams per denier and an extensibility of at least10 percent, comprising extruding a birefringent solution of the polymerhaving a viscosity of at least 70 poises, the reduced viscosity of thepolymer being at least 1.4, into a liquid coagulating bath at a spinningspeed of at least 180 metres per minute and at a pull-off ratio of atleast 1.2, and stretching the resultant fibre while the polymer is stillin the alpha configuration thereby converting the polymer substantiallyinto the beta configuration and substantially orienting the fibre alongits axis.

7. A process for the production of polypeptide fibres consistingessentially of a homopolyrner of gamma-methyl- L-glutarnate having atenacity of at least 2 grams per denier and an extensibility of at least10 percent, comprising extruding a birefringent solution of the polymerhaving a wiscosity of at least poises, the reduced viscosity of thepolymer being at least 2.0, into a liquid coagulating bath at a spinningspeed of at least metres per minute and at a pull-off ratio of at least1.2. and stretching the resultant fibre While the polymer is still inthe alpha configuration thereby converting the polymer substantiallyinto the beta configuration and substantially orienting the fibre alongits axis.

- References Cited in the file of this patent New Fibres from Proteins,Wormell, published in 1954 by Butterworths Scientific Publications,London; pp. 19 to 22, 29, and 43 to 66; copy in Scientific Library.

(a) Tanford: Physical Chemistry of Macro-molecules; published in 1961 byWiley; pp. 116 to 118 and 43744-9. (Z1) Bamford et al.: SyntheticPolypeptides; published in 1956 by Academic Press; pp. 316, 317.

1. A PROCESS FOR THE PRODUCTION OF POLYPEPTIDE FIBRES CONSISTING OF ATLEAST 90 PERCENT BY WEIGHT OF UNITS OF AN OPTICALLY ACTIVE FORM OFGAMMA-METHYL GLUTAMATE COMPRISING EXTRUDING A BIREFRINGENT SOLUTION OFTHE POLYMER INTO A LIQUID COAGULATING BATH AT A SPINNING SPEED OF ATLEAST 140 METERS PER MINUTE AND STRETCHING THE RESULTANT FIBRE WHILE THEPOLYMER IS STILL IN THE ALPHA CONFIGURATION THEREBY CONVERTING THEPOLYMER SUBSTANTIALLY INTO THE BETA CONFIGURATION AND SUBSTANTIALLYORIENTING THE FIBRE ALONG ITS AXIS.